If you're talking about "interest", you should forget it. Any form of interest eventually means unsustainable, that is exactly how traditional finance works, and the world has seen that it does not work. If you really want, you can find staking coins. proof of stake of generally just POS coins. You just need to stake the coins to mine more, look for the small interest staking so it does not lose value so easily. Big and good POS coins? Dash would be one.